In recent years, an optical communication network capable of executing data communication with a large capacity at high speeds has been expanded. It is expected that, from now on, this optical communication network will be installed not only among apparatuses, but also in apparatuses. Here, in order to achieve a printed circuit board by using optical wiring, an optical waveguide that can be formed into an array has been highly expected.
The optical waveguide is formed by a core having a high refractive index and a clad having a low refractive index, which is formed in contact with the periphery of the core so that a light signal that is made incident on the core is transmitted, while being repeatedly total-reflected by the border between the core and the clad.
Under these circumstances, recently, there have been strong demands for achieving a flexible optical wiring (in the same manner as in the electric wiring) to be installed in a bendable display and a smaller and thinner household apparatus, by using an optical waveguide. However, since the conventional optical waveguide, which is made from glass or a semiconductor, for example, like an optical coupler to be used for FTTHs, is poor in flexibility, and is not suitable for such applications. That is, film-shaped optical waveguides are demanded.
In particular, the inventors, etc. of the present application have developed an optical waveguide having high flexibility, as shown in FIG. 12, by using a further flexible material when compared with the conventional material, as the material for a core and a clad for the optical waveguide. By using this optically guided optical waveguide having high flexibility, even data transfer among substrates in an apparatus can be carried out by using optical waveguides.
In the case when this film optical waveguide having flexibility is used as an optical cable, it needs to be properly positioned, and photo-coupled with a photoelectric conversion element (light-receiving/emitting element). The light-receiving/emitting element is a device that converts an electric signal to a light signal and releases the resulting signal, and also receives a light signal and converts it to an electric signal. Moreover, upon coupling the optical waveguide to the photoelectric conversion element, a structure in which the end portion of the optical waveguide is diagonally cut off to form an optical path conversion mirror on the end face of the optical waveguide has often been used normally. In this optical waveguide having such an optical path conversion mirror, a signal light ray transmitted through the core is converted by the optical path conversion mirror in its proceeding direction, and made incident on a light-receiving element.    Patent Document 1: Japanese Patent Application Laid-Open “JP-A No. 2005-78027 (published on Mar. 24, 2005)”    Patent Document 2: Japanese Patent Application Laid-Open “JP-A No. 11-153719 (published on Jun. 8, 1999)”